1. Field of the Invention
Exemplary embodiments of the present disclosure relate to a motor for a vehicle.
2. Description of Related Art
Generally, almost every vehicle employs an electric power-assist steering system. Such an electric power-assist steering system generates an assist force based on the steering torque and the steering angle in order to enhance the steering performance of the vehicle.
That is, a steering system that assists a steering force of a vehicle with a separate power is used to enhance the motion stability of a vehicle.
Conventionally, the auxiliary steering device uses hydraulic pressure, but an Electronic Power Steering (EPS) system adapted to transmit a rotation output of an electric motor to a steering shaft via a speed reduction mechanism has been increasingly employed these days from a view point of a reduction in engine load, a reduction in weight, an enhanced steering stability and a quick restoring force.
The EPS system is configured such that an Electronic Control Unit (ECU) drives a motor in response to steering conditions detected by a speed sensor, a torque angle sensor and a torque sensor to enhance a steering stability and provide a quick restoring force, whereby a driver can safely steer a vehicle.
The EPS system is also configured such that a motor assists a torque manipulating a steering wheel to allow a driver to steer a vehicle with less power, where the motor employs a Brushless Direct Current (BLDC) motor.
The BLDC motor generally forms an exterior look by coupling of a housing with a cover member, an inner circumferential surface of the housing is provided with a stator, and the stator is centrally formed with a rotor rotatably mounted in electrical interaction with the stator. The rotor is rotatably supported by a rotation shaft, and the rotation shaft may be rotatably fixed at the housing by upper/lower bearings. Furthermore, an upper surface of the rotation shaft is coupled by an output clutch to transmit a power to a steering shaft.
However, the output clutch may repetitively receive a force applying a pressure to an inner direction of the motor, if a driver repetitively turns a steering wheel. In a case the pressing force is continuously generated, a coupling between the rotation shaft and the upper bearing may be disintegrated, which is caused by the fact that a coupling force between the rotation shaft and the output clutch is greater than a coupling force between the rotation shaft and the upper bearing. Thus, the rotation shaft of the motor may not disadvantageously make an accurate rotation if the coupling between the upper bearing and the rotation shaft becomes disintegrated or loosened.